Background

Originally found in Peru, the use of cat's claw (Uncaria tomentosa) has been said to date back to the Inca civilization, possibly as far back as 2,000 years. It has been used for birth control, as an anti-inflammatory, an immunostimulant, for cancer, and as an antiviral. The Peruvian Ashaninka priests considered cat's claw (Uncaria tomentosa) to have great powers and life-giving properties and therefore used it to ward off disease.

Multiple plant species are marketed under the name cat's claw, the most common being Uncaria tomentosa and Uncaria guianensis. Both are used to treat the same indications, although supposedly the former may be a more efficacious immunostimulant.

Cat's claw (Uncaria tomentosa) may be contaminated with other Uncaria species, including Uncaria rhynchophylla (used in Chinese herbal preparations under the name Gou-Teng), which purportedly may lower blood pressure, lower heart rate, or act as a neuroinhibitor. Reports exist of a potentially toxic Texan grown plant, Acacia gregii, being substituted for cat's claw in commercial preparations.

In Germany and Austria, cat's claw is a registered pharmaceutical and can only be dispensed with a prescription. Today, cat's claw is widely used and is one of the top herbal remedies sold in the United States despite a lack of high quality human evidence.

Evidence

DISCLAIMER:
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Allergies:
There is insufficient evidence to recommend cat's claw for allergic respiratory diseases at this time. Early studies have been conducted in Europe assessing the effects of cat's claw in patients with allergic respiratory diseases; a 10-year follow-up revealed that some patients experienced improvements.
Grade: C

Anti-inflammatory:
Cat's claw may reduce inflammation, and this has led to research of cat's claw for conditions such as rheumatoid arthritis. Large, high quality human studies are needed comparing effects of cat's claw alone vs. placebo before a conclusion can be drawn.
Grade: C

Cancer:
Preliminary evidence suggests that cat's claw may slow tumor growth. However, this research is very early and has not identified specific types of cancer that may benefit; the results are not clear. More studies are needed before a firm recommendation can be made.
Grade: C

Immune stimulant:
A few early studies suggest that cat's claw may boost the immune system, including in patients with HIV. However, results from different studies have not agreed with each other. Therefore, there is not enough information to make a firm recommendation for this use.
Grade: C

Knee pain from osteoarthritis:
Early research suggests that cat's claw may reduce pain from knee osteoarthritis. Further research is needed to confirm these results.
Grade: C